1. Field of the Invention
The present invention relates to a rail vehicle having a vehicle body defining a vehicle interior, an internal combustion engine and an exhaust system in communication with the internal combustion engine for evacuating the exhaust gases of the internal combustion engine, said exhaust gas system comprising an additive supply unit designed to supply an additive for pollutant reduction to the exhaust gas stream of the internal combustion engine, and said additive supply unit comprising a reservoir for the additive and a supply section in communication therewith for supplying the additive to the exhaust gas stream.
2. Description of the Related Art
In rail vehicles which generate their drive energy by means of an internal combustion engine, the development tasks are more and more focused on the aspect of exhaust gas cleaning, not least because of the increasingly stringent regulations with regard to the emission limits (including those for particles and nitric oxides) to be complied with. Since 2006, new legal exhaust gas regulations have gradually been introduced (so-called Level III a) in the European Union with stringent limits for new vehicles, which will be replaced in 2012 by even more stringent limits (so-called Level III b).
In order to reduce the pollutant content of exhaust gases in today's diesel engines, as a rule two different concepts are presently adopted, namely exhaust gas recirculation (AGR) or selective catalytic reduction (SCR), which may both be combined with a particle filter.
In the case of selective catalytic reduction (SCR), ammonia (NH3) and carbon dioxide (CO2) are initially obtained from urea stored as a solid or in an aqueous solution, which ammonia and carbon dioxide are then mixed with the nitric oxides of the exhaust gases and are converted in the SCR catalyst into nitrogen and water. Here, due to the simpler handling, there appears to be a tendency towards the use of the urea-water mix.
The aqueous urea solution which is, amongst others, sold under the trade name AdBlue®, is stored in an appropriate tank and is introduced through nozzles into the hot exhaust gas stream via corresponding components of the additive supply unit. In this hot exhaust gas stream it reduces the nitric oxide proportion of the exhaust gas by way of a chemical reaction in the SCR catalysts. The service temperature of the urea solution is here limited at the bottom end by its freezing point (−11° C.). At the top end, the service temperature or the storage temperature of the urea solution is limited by the temperature, at which the urea solution begins to decompose.
So far, this urea solution has predominantly been used in heavy goods vehicles, busses and passenger cars, however, even rail vehicles such as for example the motor cars of the Regio-Shuttle RS1 type of the company Stadler Pankow GmbH, Berlin, Del., have been designed with corresponding systems for exhaust gas cleaning. Especially with heavy goods vehicles, the tank for the urea solution is as a rule mounted close to the engine outside of the vehicle body on the vehicle frame. The same applies analogously to the SCR catalysts as well as to the feed lines from the tank to the SCR catalysts, which are also arranged outside of the vehicle body in a comparably unprotected manner. All of these components of the additive supply unit are thus directly exposed to environmental influences in a comparatively unprotected manner.
As a rule, these components of the additive supply unit are both subject to ambient temperatures and to the effects of the operation of the vehicle so that, as a rule, they have to be provided with appropriate thermal insulation and/or with means for heating/cooling, and they also have to be designed in an appropriately robust manner so as to be able to withstand environmental effects. As a result, a comparatively complex design of the components of the additive supply unit is required.